The present invention relates to a cutter assembly for mowing apparatus, as well as a mowing apparatus incorporaing such a cutter assembly. In particular, the invention relates to a rotary cutter assembly suitable to use a relatively thick and strong non-metallic string as a cutting flail.
Mowing apparatus are known in which a rotary assembly is provided with a coiled non-metallic string the free end of which serves as a cutting flail when the assembly is rotated. The effective working length of the flail can be lengthened from time to time when the assembly is stationary, to compensate for shortening of the working length during use. Nylon monofilament strings, which are almost completely incapable of causing any significant injury to persons or animals struck by the flailing cutting string, are often used as they can serve as effective and safe cutters. Such strings are particularly suitable for cutting or trimming along fences, walls and the trunks or stems of trees.
Typical known forms of such mowing apparatus have a rotary head member arranged to be rotated by a gasoline engine or an electric motor, the head having one or more spools detachable from or integral with the rotary head member. A length of flexible, non-metallic line is coiled about each spool and its free end swings arcuately upon actuation of the engine or motor to cut vegetation, in the manner of a flail. The initial end of a string is knotted or angularly turned at an aperture in the spool to make a tight connection therewith. However, this leads to such a disadvantage that thick and strong strings of a diameter greater than 0.10 inches (2.5 mm) can not be used due to being too strong to be knotted or angularly turned. Such strings, when turned at an aperture, make a bent with a somewhat large radius to prevent themself from orderly coiling about the spool. Strings of a diameter less than 0.10 inches (2.5 mm) are compact and less power-consumptive but not always efficient to cut heavy wild weeds. It is a fact that mowers with a dangerous metal cutter prevail in agricultural and forestal works. Therefore, there is a demand for mowing apparatus provided with a safe and strong non-metallic string capable of cutting wild weeds in the forest.
It an object of the present invention to provide an improved mowing apparatus adaptable to use a strong cutting line having a diameter greater than 0.10 inches (2.5 mm).
It is another object of the invention to provide an improved mowing apparatus having a rotary casing in the form of a spool on which a relatively thick and sufficiently long line is immediately coiled.
It is still a further object of the invention to provide an improved mowing apparatus simple in construction and easy in use.
According to the present invention, there is provided a cutter assembly for a mowing machine having a power-driven shaft, which assembly comprises a pair of members for mounting co-axially on the power-driven shaft of the mower, one of the members having a cylindrical portion secured to a disc portion of a greater diameter and the other member having a disc portion with an upstanding peripheral wall portion of a diameter greater than that of the cylindrical portion such that the two members when fitted together co-axially define an annular chamber for a coiled cutting string, the cylindrical portion having connecting means to fix the end of a cutting string thereto and the peripheral wall portion having a guide port for the free end portion of the cutting string, the connecting means having a hollow portion formed in the cylindrical portion and a slot therein in which the end of a cuting string is wedged, the cutting string made of a high-polymer synthetic material having a diameter greater than 0.10 inches (2.5 mm), and there being means coupling the two members together for simultaneous rotation releasable to allow relative rotation by axial separation of the two members and resilient biassing means urging the two members together to the coupled disposition.
Preferably, the cutting string has such diameter of from 0.11 inches (2.8 mm) to 0.13 inches (3.5 l mm) that is strong and flexible to the extent that it is sufficient to cut heavy wild vegetation but substantially incapable of causing damage or injury if it contacts persond or animals.
A preferred embodiment of the invention has connecting means provided with a hollow window formed in the inwardly thick wall of the cylindrical portion and a thin plate inserted in the window. The thin plate is formed with a triangular slot with an angular apex directed towards the direction of winding of the string. The inwardly thick wall has on the side pointed by the apex an outer bevelled surface and in the opposite side an inner guide plate projecting inwardly towards the apex.
In a preferred emboldiment of the invention, the two members are mounted on a shaft which is itself attachable co-axially on the output shaft of the mowing machine, the shaft being drivingly connected to the one member. So that drive may be imparted to the one member, the shaft advantageously has a polygonal section which is received in a correspondingly-shaped recess in the one member. A spring is mounted on the shaft between the other member and a washer releasably mounted on the end portion of the shaft remote from the one member, so as to bias the other member towards the one member. For this arrangement, when the washer is dismounted from the shaft, the other member as well as the one member if required, may easily be removed from the shaft, allowing replacement of a string and the coiling of the string around the cylindrical portion.
A preferable form of coupling means comprises a plurality of equi-spaced projections upstanding axially from the peripheral wall portion of the other member and receivable in corresponding recesses formed in the one member. The other member may have a circular central aperture fitting on a corresponding section of the shaft. The other member is depressible from the one member against the bias so as to be rotatable with respect to the one member. Accordingly, additional string may be payed out by rotating the one member relative to the other member so as to alter the effective working length of the string.
The apparatus of the invention contains neither spools separated from a rotary casing nor locking means therefor to be operated, and therefore is simple in construction and easy in use. The rotary assembly has a large inside space devoted to line-storage and so a long cutting line relative to its size can be stored.
The invention itself, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.